Phase change material device using a sidewall liner and methods for forming the same

A device structure comprising:

• a bottom electrode and a heater element formed within a dielectric material layer;
• a layer stack including a bottom liner layer, a phase change material portion comprising a phase change material, and a top electrode;
• and
• at least one sidewall liner located on at least one sidewall of the layer stack and comprising a material having an electrical conductivity that is higher than an electrical conductivity of an amorphous phase of the phase change material.

A device structure comprising:

• a programming transistor located on a substrate;
• a bottom electrode and a heater element formed within a dielectric material layer, wherein the heater element is electrically connected to an electrical node of the programming transistor;
• and
• a phase change memory cell comprising a layer stack including a bottom liner, a phase change material portion comprising a phase change material, and a top electrode, and further comprising at least one sidewall liner located on at least one sidewall of the layer stack,
• wherein the programming transistor is configured to program the phase change memory cell into at least three different resistive states by applying at least three different programming pulse patterns to the heater element.